Agree with all above...but IMO most likely embedded teeth...one or more could do it. Snake teeth are hard to see to remove too, they tend to be on the translucent side,
you might let your doctor know that this "splinter" might be harder to see.Snake teeth break off easily, especially when we reflexively jerk away, so you could have
literally any number of teeth in there. I think a plain old infection or reaction to saliva would have happened much faster...I personally vote for "snake teeth" as the time
frame fits...it takes time for your body to respond & try to push them out.